Manufacture of spinning nozzles



March 31, 1959 M. BUR'KHARDT ETAL MANUFACTURE OF SPINNING NOZZLES FiledFeb. 24, 1953 v V, x% 1 INVENTORS MAX BURKHARDT EMIL GRAFRIED BYGRETELORE RAUNECKER ne Hum Maw R0 CAL ATTORNEYS United 2,879,676MANUFACTURE OF SPINNING NOZZLES Max Burkhardt, Hanan (Main), EmilGrafried, Grossanheim (Main), and Gretelore Raunecker, Hanan (Main),Germany, assignors to W. C. Heraeus G.m.b.H., Hanan ma Wholly syntheticfilaments, more particularly filaments of polyamides and similarpoly-condensates and other polymer substances, are generally produced byforcing the ready-prepared substance in a molten or plastic statethrough spinning apertures, the substance then solidifying to formfilaments when cooling down. This procedure places much higherrequirements upon the spinning elements than the methods known in themanufacture of rayon filaments and of viscose wool. The temperatures lieup to 200 higher, and the pressures exceed those of the earlier methods.The spinning apertures, which may for example have, at the outlet sideof the spinning disc, a diameter of one tenth, or a few tenths, of amillimetre, must retain their accurate dimension at these relativelyhigh temperatures and pressures. Although the spinning apertures areadditionally exposed at these high pressures and temperatures, toconstant friction by the extruded synthetic resin substance, they mustretain their high gloss and must not become rough. These qualities ofthe surface of the spinning apertures must also not get lost duringcleaning with concentrated acids.

In order to comply with these high requirements, it has already beenproposed to provide spinning discs consisting of acid-resistant steels,equipped with insertion pieces of precious metals in which fine boresare drilled to form the spinning passages. Furthermore, it has alreadybeen proposed to provide the spinning apertures with a chromium coating.This latter suggestion, however, is extremely difficult to carry out inpractice, as will be readily appreciated by those skilled in the art.

When using preformed insertion pieces of precious metal, the diameter ofthe spinning apertures cannot be reduced below a certain limit, and moreparticularly it is impossible to produce in this manner spinningapertures of certain desirable shapes, for example, long spinningapertures of fine cylinder shape. The present invention has for anobject to enable spinning nozzles suitable for the production of whollysynthetic filaments to be produced having spinning passages of any shaperequired by the spinning technique and which, at the same time, may beproduced directly with the desired high-gloss polish.

With this object in view, according to the invention, the spinningpassages are provided in the spinning discswhich, in a known manner, mayconsist, for example, of steel plates of 6 to 10 mms. thicknessby thefollowing method: I

First a core is made having the shape of the spinning aperture to beproduced. On this core there is deposited a layer of hard metalresistant to nitric acid and having a thickness of, for example, 0.5 to3 mms., which may be done by a known method. We have found particularlysuitable hard base metals, such as chromium or chromium alloys, themetal being preferably galvanically deposited on the core. If the coredoes not consist of metallic material, a thin intermediate metal layeris first applied, for example, by vapour deposition in a vacuum,whereafter the hard chromium coating is gales atef r" 2,879,676 PatentedMar. 31, 1959 plied to the core may also itself be deposited by other 3methods, e.g., by high vacuum vapour. deposition, cathode sputtering, orgas decomposition.

The material for the core is so selected that it may be removed.chemically without damage to the metal deposited thereon. Preferably thecore is made of an iron-nickel alloy; this alloy may readily be removedfrom ashell of chromium by being dissolved in nitric acid.

The shell body thus obtained is then inserted into a correspondingaperture provided in the spinning disc and may, if desired or necessary,be further secured therein by known methods, such as pressing, swaging,soldering or brazing; a firm seal at the edge may also besensured byadditional galvanic deposition of'metal', for example of chromium. Ifthe core, the shape of which corresponds to the desired spinningaperture, is not of a's'lim cone shape, it is advisable'to grind theshell body externally to a slim cone shape and to insert it intoacorrespondingly shaped aperture of the spinning disc, thereby ensuringaparticularly firm seating.

In order that the invention may be more readily understood, it will nowbe described by way of example with reference to the accompanyingdrawing, in which:

Fig. 1 is a cross-section of a small portion of a spinning disc.

Fig. 2 is a similar section of the core for a spinning nozzle.

Fig. 3 similarly shows the core with the shell deposited thereon, and

Fig. 4 is a view similar to Figure 1 showing the corresponding part ofthe completed spinning disc equipped with a nozzle.

Referring now to the drawing, a spinning disc A, of which a smallportion is shown in Figure 1, and having a thickness of 6 mms. isdesired to be provided with spinning apertures having the shape shown inFig. 2. The spinning apertures in this example have a hyperboloidalsection. The diameter may, for example, be

a 1 mm. at the point of entry, the aperture being reduced at the outletpoint to an approximately cylindrical passage having a diameter of 0.12mms.

According to the invention, first a core as shown at B in Fig. 2, ismade of a metal soluble in nitric acid, for example of an iron-nickelalloy. On to this core a hard chromium layer C (Figure 3) having thethickness of 2 mms. is then galvanically deposited. This layer is grounddown externally along the circumference D to produce a slim cone fittinginto the conical aperture of the spinning disc A (Figure 1).

Finally, the shell C is, after the core B has been removed by beingdissolved in nitric acid, inserted according to Figure 4, into theconical recess of the spinning disc A having a thickness of 3 to 6 mms.and, if necessary or desired, may be additionally secured and sealed byone of the above-mentioned methods.

In this manner spinning apertures may be produced without difiicultyhaving a cylindrical passage with a diameter of as little as 0.1 mm. oreven less, a problem which cannot be solved with drilled precious metalinsertions. Moreover, the inner surface of the spinning passages will beproduced directly with a high-gloss polish provided only that the core,which can be readily machined or otherwise worked from its outer side,is made with a high polish. This method also is not limited to the useof precious metals thus permitting the utilisation of the very greathardness and chemical resistance of chromium. It should be particularlystressed that the illustrated form of the spinning aperture is onlygiven by way of example and that, in fact, the new method makes itpossible for the spinning apertures to be produced having any of avariety of shapes desirable for reasons of the spinning technique andconstituted, for example, by a combination of cylindrical and conicalparts, or having a vertical section composed of curves of differentnature. The fine spinning passages may also be arranged to projectbeyond the :outer surface of the spinning discs thus ensuring furtheradvantages in special cases.

We claim:

1. A method for the manufacture of spinning nozzles, wherein spinningapertures have a hyperboloidal section, comprising making cores havingthe desired hyperboloidal shape of the spinning apertures to beproduced, depositing on each of the cores 2. layer of chromium ofsnflicient thickness to form a shell wherein the outer surface may e shp d o a desired f m i din the surfa e i t h l to a u a nt o nisa term,em n the cores from the shells by dissolving the same, providingspinning discs having openings of conical form suitably shaped forreceiving the shell bodies, inserting the ground chromium shell bodiesinto the openings of the discs, and securing said shell bodies in saidopenings.

2. A method for the manufacture of spinning nozzles,

wherein spinning apertures have a significantly curved section,comprising making cores having the desired curved shape of the spinningapertures to be produced, depositing on each of the cores a layer ofchromium of sufficient thickness to form a shell wherein the outersurface may be shaped to a desired form, grinding the outer surface ofthe shells to a regular continuous conical form, removing the coresfrornthe shells by dissolving the same, providing spinning discs havingopenings of conical form suitably shaped for receiving the shell bodies,inserting the ground chromium shell bodies into the openings of thespinning discs, and securing said shell bodies in said openings.

References Cited in the file of this patent UNITED STATES PATENTS1,604,216 Brainin Get. 26, 1926 1,654,936 Jones Jan. 3, 1928 1,672,644Hoffman et al. June 5, 1928 1,708,715 "r-'--"."--..'---'r'" re--,Qr' 1.1 1 6 9 r Ave 44 2 0 8 0 Prunes A r .2 3,408,713 Webb s Oct. '1, 19462,422,612, Home June 17, 1947' 2361,64!) Hallberg .Feb. 15, 1949

